Abstract
BackgroundReestablishment of apex predators influences the availability and distribution of biomass for scavengers and can therefore be an important agent for structuring species communities. We studied how the re-colonization of the Scandinavian Peninsula by wolves (Canis lupus) affected the amount and temporal variation in use of moose (Alces alces) carcasses.Methodology/Principal FindingsWe compared the availability of biomass from remains at wolf kills with those killed by hunters, vehicle collisions and natural death. Movement-triggered cameras monitored patterns of use on wolf kills and remains from hunter harvest by scavengers (n = 15 276) in relation to time of year, available carcass biomass, time since the death of the moose and presence of wolves. Remains from hunter harvest were the largest food source for scavengers both within wolf territories (57%) and in areas without wolves (81%). The total annual biomass available were similar in areas with (25 648 kg) and without (24 289 kg) wolves. Presence of wolves lowered the peak biomass available from hunter harvest in October (20%) and increased biomass available during December to August (38–324% per month). The probability of scavengers being present decreased faster with time at remains from hunter harvest compared to wolf kills and both the probability of being present and the number of visits by scavengers to wolf kills increased as the amount of biomass available on the carcass increased.Conclusions/SignificanceWolves reduced the seasonal variation of biomass from moose carcasses and most important increased it during spring. Scavengers also visited wolf kills most frequently during spring when most scavenging species have young, which may lead to an increase in survival and/or reproductive success of scavengers within wolf territories. This applies both for abundant scavenging species that were the most frequent visitors at wolf kills and threatened scavengers with lower visit frequency.
Highlights
Scavenging is a common phenomenon among terrestrial vertebrates and almost all predators are scavengers to some extent [1]
In this study we focused on modelling the average impact of wolves on the temporal availability of biomass to scavengers in order to compare the importance of wolf predation with other causes of moose mortality
We found only minor differences in the number of species visiting wolf kills compared to remains from hunter harvest, but wolf kills tended to have a higher number of visits than remains from hunter harvest, even during peak harvest month (October)
Summary
Scavenging is a common phenomenon among terrestrial vertebrates and almost all predators are scavengers to some extent [1]. In the temperate zone scavenging vertebrates mainly consume carcasses during the cold season [1] when other food sources become scarcer with the progress of winter [2]. Humans unintentionally provide food for scavengers through hunting and wildlife-vehicle collisions, but these sources of biomass have large temporal and spatial variations. Remains from hunter harvest are generally available only for a few months during the hunting season in autumn [5], and road density will affect the number of ungulate-vehicle collisions [6]. The temporal and spatial distribution of carcasses to scavengers will depend on the predominant cause of mortality in ungulate populations [1]. Reestablishment of apex predators influences the availability and distribution of biomass for scavengers and can be an important agent for structuring species communities. We studied how the re-colonization of the Scandinavian Peninsula by wolves (Canis lupus) affected the amount and temporal variation in use of moose (Alces alces) carcasses
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